Environment

Crop survival in a hot climate

Climatic uncertainties: A farmer applying fertiliser to his rice fields in Medak district, some 60km from Hyderabad. Monsoon rains in India this season (June to September) has been 35% below average, causing rice planting to be 18% lower than for the same period last year. Climatic changes are affecting food cultivation worldwide. - AFP

In a world that is warming too fast, farming methods will have to change.

CHANGES in temperature, precipitation and wind patterns that are associated with climate change are expected to affect crop production – hence, food security is a looming issue.

Global warming is projected to alter the production of rice, wheat, corn, soybean, and potatoes – diet staples for billions of people around the world. Which is why agronomist Dr Ajit Singh contends that it warrants global concern.

“Food crops that we rely on most are sensitive to climate change as not only are the temperature and moisture of the surroundings affected, but those in the soil too. Simulation studies project a 20% and 30% decrease in global crop production, attributed to climate change, by 2020 and 2030,” says the associate professor at the School of Biosciences at University of Nottingham Malaysia Campus at a talk titled “Effects of Climate Change on Food Crop Production”.

“The growth stage is important as the crop will be exposed to drought or heat. Flowering or fruiting can be extremely sensitive, and the temperature and rainfall changes induced by climate change will interact with atmospheric gases, fertilisers and soil organic matter to produce unanticipated responses,” he says.

To illustrate how climate change correlates with crop output, Dr Ajit shares data from studies in three different regions: the African arid climate in Niger Republic, the semi-arid climate in Sokoto, Nigeria, and the tropics in Alor Star, Kedah. Based on data from the Meteorological Centre in Niamey, the Niger Republic – which has an annual rainfall of less than 500mm – recorded no significant increase in temperature between 2003 and 2012. Complete data on crop production could not be obtained but it showed mixed responses to temperature changes.

“The lack of data meant that we could not arrive at a conclusion but it gave us an idea on the kind of crops that are resilient or not affected by temperature increases. We found the hungry rice (Digeteria exilis) and groundnuts to be more resistant. This will prove useful when it comes to selection of crops in future.”

In the semi-arid climate of Nigeria where the annual rainfall is between 600mm and 800mm, 20 years of data from the Energy Research Centre in Usmanu Danfodiyo University in Sokoto showed an annual average increase of 0.04°C from 1991 to 2001. Rainfall remained unchanged during that period. Crops like onions, tomatoes and peppers were found to be suitable for the dry season when temperatures were lower while rain-fed groundnuts appeared to be more resilient.

“In Alor Star, Kedah, 30 years of data gathered between 1981 and 2010 showed an annual average increase in temperature of 0.03°C. If we assume that there were no significant changes in rice production from either agricultural technology or a newly-introduced variety during this period, the linear trend analysis between temperature and rice yield demonstrated a positive response to the increase in temperature during this period,” says Dr Ajit.

He says there are various agricultural practices to offset the adverse effects of climate change on crop production and soil, such as mulching, that will help with water conservation and soil fertility, and crop rotation, which contributes to sustainable cultivation.

“Crop rotation or inter-cropping is an effective, natural pest control method since increased pest attacks are likely to arise from insects that reproduce from a lengthened breeding season and which multiply and thrive in hotter temperatures,” he explains. He adds, however, that mono-cropping (growing the same single crop every season) is commonly practised in Malaysia and other parts of developing Asia because of profitability in the short term. Cultivation of papaya, pineapple and oil palm are examples of mono-cropping systems.

Climate change will alter the production of major food crops, according to Dr Ajit Singh of the University of Nottingham Malaysia Campus.

“Continuous cropping of the same plant results in accumulation of pests and diseases that are difficult to control. The organisms causing the disease are host-specific, that is, they survive on one plant only. If another plant is cropped the following year or after five to six years in rotation, the pests eventually die because they cannot survive on the new host. Crop rotation and inter-cropping were practised in the past but farmers nowadays do mono-cropping using high-value crops to reap more profits.”

As ridding pests by using chemical pesticides will add to carbon emissions, Dr Ajit says organic control should be advocated. He explains that although carbon dioxide is an essential compound in photosynthesis which also increases water-use efficiency in plants, these positive effects of the gas can be nullified by related increases in moisture stress caused by low rainfall and high temperature. Also, increased cloud cover due to higher global temperature is projected to limit the photosynthesis process and result in decreased crop production.

Dr Ajit says other ways that farmers can mitigate the effects of climate change on crops is to improve crop varieties to ensure a diversity of plants, and to conserve germplasm.

“With rising incidences of drought, water-use efficiency has to be optimised. Crop condition, too, has to be monitored, especially with the presence of weeds which are better-adapted to arid conditions than crops, and which will lead to increased competition for moisture, nutrients, and light.”

For food security to be guaranteed, he says people must improve the way they manage agricultural systems. As most models observe climate change on a global scale, a customised, local model variation will be needed for people to come up with adaptation measures in Malaysia. The Food and Agriculture Organisation has urged for a shift to climate-smart agriculture. Various crops are being planted in different regions. One example is the agro-forestry system in 120,000ha on the slopes of Mount Kilimanjaro, Tanzania, where coffee is grown in between forest trees.

In Peru, 3,500 families are helping to conserve 177 varieties of potatoes (an essential food crop for Peruvians) to protect genetic diversity. In Nigeria, farmers bury urea briquettes in rice fields, which raised yields by 25% as well as reduced nitrogen release by 40% and usage of urea by 25%. The technique also prevented loss of fertiliser through surface runoff.